There exists a need in the medical arena to know the surface contour of a feature on a living subject without coming into contact with the subject. Determining, the contour of a biological surface is especially important in situations in which contacting the surface to be measured is not desired. In particular, contact with the biological surface may not be desired due to, the measuring means changing the contour of the surface, the contour changes are small or difficult to measure consistently, contact with the surface may results in the transmission of bacteria or other infectious agents.
An example of this need occurs during the replacement of heart valves or other vascular grafts. During such transplants it is important that the diameter and size of the transplant tissue be approximately that of the vascular tissue in the recipient site. Typically these measurements are conducted during surgery by comparing the diameter of the recipient""s vascular tissue with a size chart. A precision caliper can not be used in such situations because of the difficulty in sterilizing the measuring device. As a result, the attending surgeon can only make an approximation as to the diameter of vascular tissue at the graft site. In a similar manner the proper measurement of the vascular tissue at the donor site is difficult because of the pliable nature of the tissue. Although in many cases an estimated measurement of the recipient site tissue and the donor tissue is suitable, a more precise fit could lead to better and more rapid healing.
The present invention provides for a method of making contour measurements in a precise manner without contacting or otherwise disturbing the biological surface of the tissue. Generally the method involves the measuring the contour of a biological surface without physically contacting the biological surface. Such a method includes defining a reference plane relative to the biological surface. The reference plane is defined by the x axis and y axis of a mechanized x-y positional axis means coupled to an optical distance measuring means. A first distance from the reference plane to the biological surface is measured using the optical distance measuring means and a value of the first x axis position and a value of the first y axis position of the optical distance measuring means in the reference plane and the first distance are stored in a register of x axis position, y axis position and distance. The optical measuring means is then moved a predetermined distance along the x-axis, the y axis or both to a second position and a second distance from the reference plane to the biological surface is measured using the optical distance measuring means. The values of the second x axis position, the second y axis position and the second distance are stored in a register of x axis position, y axis position and distance. A relative height value may be then calculated by subtracting the first distance from the second distance. A plotting the x axis position, y axis position and relative height value on an orthographic x, y, z coordinate system results in a three dimensional plot of values that is representative of the contour of the biological surface.
The above described method may also include moving the optical measuring means to a series of predetermined positions in the reference plane; measuring the distance from each predetermined position to the biological surface using the optical distance measuring device; storing the x axis position value, the y axis position value and the distance for each predetermined position in the reference plane in a register of x axis position values, y axis position values and distance values; and subtracting the first distance from the distance for each predetermined position to give a relative height value. The values of x axis position, y axis position, and relative distance may be stored in the electronic memory of a computer thereby generating a data set of values which may be mathematically manipulated. In one preferred embodiment, the optical distance measuring means is a laser based distance measuring device. The biological surface may be a wound bed or a dermal surface. or it may be vascular tissue including heart valves, veins and arteries.
These and other features of the present invention are more fully set forth in the following description of illustrative embodiments of the invention.